Large touch-sensitive area with time-controlled and location-controlled emitter and receiver modules

ABSTRACT

The invention enables the realization of an optical and electronic structure of a touch-sensitive area on any flat display surface such as a monitor. The optical structure does not require any additional optical components such as lenses. Laser diodes are likewise not required for the operation of a structure of this type. Large distances and, nevertheless, high sensitivity and high resolution of the touch-sensitive area are accomplished by a novel time-control and location-control of both the emitter diodes as well as the receiver diodes or receiver photo-transistors. If still or moving images are displayed on the surface, the invention can be used as a touch screen and can interactively control the display. A central module simulates a computer mouse and a keyboard.

The invention relates to the optical and electronic structure of a verylarge (possibly over 0.04 m², typically: >1 m²) touch-sensitive area(also called a touchscreen) on any transparent surface (monitor), whichis used to build multi-active display windows, multi-active boxes,information terminals, or security systems, e.g., in the form ofpersonnel filters. This invention describes the application of amulti-active display window, whose entire area, up to 8 m×8 m, can beconfigured interactively for the first time. Here, the resolution of thescan equals ±1.5 mm.

For the application as a multi-active display window (FIG. 1), afocusing screen, projection film, or another projection surface (2),which replaces part of or the entire decoration (8), is set up behindthe display window panel (1). On this surface, a large-area image isprojected (rear projection) from behind by means of a known video anddata light projector (7). These images are typically generated by acontrol computer. At the border of the display window panel, avandalism-proof coating is applied from the outside. This contains aspecial infrared (IR) emitter and receiver module arrays (3, 4, 5, 6),which cover the display window (the touch-sensitive area) with aninvisible light-barrier curtain. From the front, the user can point to acertain area of the image (user input). This area is identified by thestructure according to the invention described in this patentspecification and forwarded to the control computer. This computer cancontrol the further flow of images and graphics corresponding to theuser input. Thus, an interactive, i.e., user-controlled, presentation ispossible. Here, this user input need not absolutely lie on the areagiven by the rear projection; instead, a separately designated area(e.g., a keyboard or trackball) can also be on the touch-sensitive area.Furthermore, the described detection structure can also be applied toother optical systems and image generators, which generate images onsurfaces (plasma screens, large monitors, LCD monitors, rear-projectionboxes, etc.).

The presentation processed in the control computer can consist of, e.g.,an Internet presentation. The multi-active display window can then befunctionally compared with a computer mouse and its navigationproperties. Thus, for the first time economical (without personnel andaround the clock) information and advertisements can be provided for anysupplier at locations in cities that are heavily frequented bypedestrians.

For the current state of the art, touch-sensitive surfaces up toapproximately 40″ (touchscreens) are realized preferably in the type inwhich a film or a number of thin conductive threads on the image surfacedetects the user input (touch) because an electrical property of thefilm or the thread (e.g., resistance, capacitance, field strength)changes when touched, and this change is converted into the exacttwo-dimensional position of the user input by evaluating the separatelydetected horizontal and vertical electrical signals.

The disadvantages of these methods are the following:

-   -   1) The cost of the structure greatly increases with the size of        the touch-sensitive area. Surfaces over approximately 0.5 m²        thus cannot be realized economically.    -   2) The accuracy of the touch detection decreases with larger        surfaces.    -   3) The described methods are unsuitable for use in public areas,        because they are not vandalism-proof. This means that they can        be easily destroyed and can no longer fulfill their intended        function due to outside actions of a willfully destructive        nature.    -   4) Most solutions of the state of the art require additional        layers over the projected image and thus attenuate the        brightness of the image.

Other possibilities include the acoustic (ultrasound) detection of theinterrupt, wherein fewer emitters/receivers are necessary than fortwo-dimensional networks. However, this technology is reliable only upto touchscreen sizes of approximately 1.5×1.5 m² and shows disadvantagesfor the reliable detection of user input in the edge regions.

There are also active detection systems. Active means that the user usesa special, active transmitting pointing device in order to perform theuser input (flip-chart). This system is not suitable if anonymouspersons are to benefit from the interactivity, e.g., of the multi-activedisplay window.

In addition, for small touchscreens (e.g., in automatic bank machines),detectors based on infrared emitters and receivers are used. Here, thetouch-sensitive surface is covered with invisible IR radiation and theinterruption of a light barrier is detected. The emitters and receiversare turned on permanently. Usually, additional lenses are used forincreasing the light-beam focusing for such structures. Therefore, onlysmall surfaces (<0.1 m²) can be detected, because for greater distancesfrom the emitter units to the receiver units, strong cross-couplingprevents the detection of the user input and also the light intensity ofthe diodes is no longer sufficient to achieve reliable detection.

It is known, e.g., for infrared light-emitting diodes (IR-LED) fromremote controls, that LEDs can be operated in a pulsed mode up to pulseduty factors of 1:100. This means that the LED is turned off one-hundredtimes longer than the time during which it is turned on (and thus emitslight). Here, pulse sequences (bursts) with rectangular signals areforwarded to the emitter, which produce a more or less sinusoidal lightstream based on their self-capacitance and the pn-junction properties.The electrical current during the short on period can then equal100-times the nominal continuous current without significantly affectingthe life of the LED. Thus, considerably higher peak powers of the lightradiation can be achieved in a short time period than would be possiblefor continuous operation.

It is further known that IR-LEDs and IR receivers (IR-sensitivephotodiodes, phototransistors, or photoresistors) can be used in lightbarriers. Here, the interruption of the optical connection betweenemitter and receiver (when the emitter and receiver “are looking at”each other) or the formation of the optical connection (when the emitterand receiver see each other only if a third object reflects the emittedlight) is detected and, e.g., it is determined whether a person haspassed through a certain space or whether a person is located in frontof a certain point in space.

An embodiment of the invention is explained in more detail withreference to the enclosed drawings. Shown are:

FIG. 1, a schematic structure of a multi-active display window,

FIG. 2, a block diagram of a large-area, interactive projection,

FIG. 3, the structure of the time-controlled and position-controlledlight barriers.

The disadvantages mentioned above of previous touchscreen solutions forlarge surfaces do not occur for a configuration of the touchscreenaccording to the invention. In connection with a rear projection bymeans of contemporary high-power LCD or DMD video and data projectors,large display windows can be transformed into multi-active projectionsurfaces (FIG. 1), which fulfill the following properties:

-   -   1) Economical provision of the display window with a        touch-sensitive surface.    -   2) Vandalism-proof structure.    -   3) Reliable detection of a user input for a finger width greater        than 10 mm (small children) with a position resolution of ±1.5        mm without any light loss of the projection.    -   4) Completely automatic day and night operation possible due to        high-power, remote-control capable projectors.

According to the invention, these requirements are fulfilled bydetecting the user input through electromagnetic (typically in theinfrared range of the spectrum) emitters and receivers, which arearranged in the horizontal and vertical direction and which arecontrolled in a suitable way in a time-sequenced and position-dependentpattern. These transmitters and receivers are each arranged separatelyin modules (transmitters and receiver modules FIG. 3, 300, 310), whichcan be arranged in series in principle in an arbitrary amount (FIG. 2,100, 110, 120, 130). These modules are attached on the outside aroundthe touch-sensitive area (190) to be defined, wherein the modules can bemounted at a large distance to the borders of the area (up to 8 m fromeach other), which creates the ability of “hiding” these components interms of construction. Because the modules are installed in stablealuminum, steel, or diecast housings, this arrangement isvandalism-proof. The emitter and receiver modules 300, 310 are arrangedopposite each other and “look” out over nearly the entiretouch-sensitive area 190 (the distance from the display window surfacehere equals approximately 0.5 to 3 cm). Each module (300, 310) has itsown microcontroller, which is arranged in the module itself. The entirearrangement represents a multiprocessor system. Also, the central module140 has a microcontroller with greater capability relative to the modulecontrollers (greater RAM capacity, higher clock frequency, largerflash-RAM). The emitter modules 300 receive their control signals fromthe central module 140. The measurement signals of the receiver modules310 are analyzed statistically and then transmitted to the centralmodule 140.

The central module 140 assembles the entire interactive surface andrecognizes a relevant user input. This input is output, e.g., in aspecial protocol (e.g., standard serial interface for a mouse) to thePC. Other output types, such as x-coordinates, y-coordinates (forspecial consoles), or PS2-mouse emulation can be set by the attached PC.The central module allows the implementation of arbitrary mouseprotocols or serial transmission protocols based on the microcontrollercircuit. The data is transmitted to the control computer 220 controllingthe presentation.

A preferred configuration of the invention is described in the following(FIG. 2, FIG. 3):

The touchscreen consists of IR-emitter and IR-receiver modules (300,310), which are arranged together into corresponding horizontal andvertical emitter and receiver module arrays (100, 110, 120, 130). Here,the number of active emitter modules in the horizontal (or vertical)direction n (or m) must agree with the number of active receiver modulesin the horizontal (vertical) direction. Here, m can not equal n. Thus,any rectangular area 190 can be defined. In the preferred example, n, mshould not be greater than 16. For example, for a structural modulelength of 16 cm (16 emitters 300 or receivers 310 are assembled on amodule and the distance of the emitter diodes or receiver transistors toeach module is 10 mm), user inputs on a maximum surface area of2.56×2.56 m² (6.55 m²) can be detected in this embodiment. In principle,larger areas with a configuration according to the invention arepossible. The emitter and receiver module arrays (100, 110, 120, 130)must not be mounted directly on the touch-sensitive area 190, butinstead can feature a distance, which in principle is arbitrarily large,from the area (FIG. 2). The corresponding two emitter and receivermodule arrays (which in turn consist of n or m modules) are connected toa central module 140. In the preferred configuration of the invention,the central module 140 automatically notices how many modules make upthe units in the x-direction (horizontal) and y-direction (vertical). Inthis preferred configuration, next to the active region 190, which ispredetermined by the size of the projected image, yet anothertouch-sensitive area 170 can be defined, which can be used as a keyboardand/or trackball for data input to the control computer (PC) 220.Therefore, in the total possible touch-sensitive area, allowed zones(180 and 170) and not-allowed zones (175) are created. The connectionfrom the central module 140 to the control computer (PC) 220 is realizedin this configuration by two interfaces, one functions as a mouse 150,one as a keyboard 160, and by a keyboard, mouse, and monitor changeoverswitch 210. An additional mouse 250 and an additional keyboard 240 canbe installed for fitting the entire system directly at the site of thecontrol computer (PC) 220, which can be in a different room.

In the following, the type of control of the individual emitter diodesand receiver phototransistors (320, 330) is described. Instead of thephototransistors, naturally other optical receivers, such as, e.g.,photodiodes or photo-elements can also be used. The control isdistinguished by the following fundamental properties:

-   -   1) Only one opposing pair 340 of emitter/receiver diodes of a        emitter/receiver unit are ever turned on. This means that an        emitter diode emits (in general) IR light, while in this time        period t_(D) only the opposing receiver diode is turned on (only        its signal amplifier amplifies the incident signal). After a        certain time Δ_(diode) this pair is turned off and the next is        pair turned on. After one cycle (scan) over all the diode pairs        is completed, the cycle begins again with the first pair. It is        useful to scan the horizontal and vertical diodes simultaneously        (so that two emitter diodes and two receiver diodes are always        turned on, one from the horizontal and one from the vertical        emitter/receiver unit). The sequence of diodes to be turned on        is completely arbitrary, but for the sake of control simplicity        they should be turned on in series. A typical value for        Δt_(diode) is currently around 200 μs. A faster or slower        control for other applications (e.g., security technology,        monitoring areas) is possible. Thus, using a maximum of 16        modules each with 16 diodes produces 256 diodes per        emitter/receiver unit and a time of approximately 50 ms for one        scan (this corresponds to a total scanning frequency of        approximately 20 Hz).    -   2) The paired operation of the emitter and receiver diodes        spares the use of expensive optics for focusing the emitted        light. These would otherwise be necessary to prevent        cross-coupling between the receivers over such large distances.        For the same reason, simple IR-diodes with small beam angles are        sufficient. No laser diodes are used (which would be more        expensive many times over).    -   3) During the short on time Δt_(diode) of an emitter diode 320,        this diode is operated at a multiple of the nominal continuous        power (current-regulated or voltage-regulated). The light        emission during time Δt_(diode) is thus a multiple over its        nominal continuous light power. Because each IR-LED is turned        off during the remaining time of a scan, this means no        restriction on the life of the diodes. For this reason, the        distance of the emitter and receiver units to the        touch-sensitive surface can be large (up to 8 m total distance        has already been demonstrated). Because the emitter and receiver        arrays are to enable the scanning of a large sensitive area, a        normal pulsed solution, like those in remote controls with        normal rectangular voltage level control or even sinusoidal        control, is no longer possible. Here, the diode must be        considered as a component with depletion layer capacitance,        charge carrier lifetime, and charge carrier mobility. These        factors produce the necessity of generating massive saturation        at turn on through the turn-on voltage amplitude and through a        build-up time that lies in the region of a few ns. To achieve        such control behavior, different methods, such as the use of        high-power, fast switching transistors or corresponding logic        with re-differentiation and amplification can be used. Through        this saturation, no pulse sequence in the kHz range is possible        for the normal LED, because there are too many charge carriers        in the pn junction. A pulse sequence with this control produces        a single flash of light, which fades in the range of μs after        turning off the pulse sequence. To prevent this property, the        emitter diode must be discharged of charge carriers again        directly after saturation. For this purpose, there are various        possibilities, e.g., the use of an additional discharging        transistor or simply a parallel load resistor. The result is the        generation of short, very intense flashes of light, which are        emitted as a sequence (burst) and which are used later in the        receiver as the basis for a high signal-to-noise ratio. The        microcontrollers in the emitter modules permit both controls to        be set individually in order to minimize possible reflections on        the display window panel or projection plane. In the preferred        configuration of the invention, according to the size of the        interactive surface, 10-15 pulses are emitted per burst.    -   4) During their on time, the IR-LEDs 320 are operated not at a        constant power, but instead in the so-called burst-mode. This        means they are operated with a frequency f, which clearly lies        over the frequency of the relaying of the diodes f>1/Δt_(diode).        Typically, this frequency lies in the kHz range.    -   5) The amplification circuit of detectors 330 in the receiver        unit features a high attenuation (low amplification) for        frequencies not equal to the burst frequency f, but a low        attenuation (high amplification) at the burst frequency f.        Therefore, ambient lighting affects (daylight, 50 Hz ripple        frequency from power-line lamps, etc.) are effectively        suppressed. The input circuit of the receiver, however, has no        normal filter (LC, RC) as a working resistor, but instead uses        only an inductor as a working resistor. Therefore, two        significant advantages are produced: first, disruption by        constant light (daylight, street lamps) or light with amplitude        modulation in small frequency ranges (50 Hz, 100 Hz) is no        longer possible. In this case, the coil acts as a short circuit.        Second, the operating point of the phototransistors even for        strong incident sunlight is not shifted so far that the usable        signal can no longer be detected. For burst analysis, no filter        or PLL system is used. After the build-up time, an integrator is        turned on, which permits continuous average value formation. The        integration time has a ratio of 1:3 to the total time of one        burst. By means of a comparator, a nearly 100% detection        likelihood of the interrupts of the light barrier is obtained        for large distances between emitter and receiver. The receiver        components can be influenced in their sensitivity with the aid        of the microcontroller by the beginning of the integration and        by the period of the integration relative to the burst time.        This allows a flexible and automatic adaptation to the total        distance of the emitter and receiver arrays.    -   6) For further increase of the reliable detection also of        narrower interrupts and the resolution capability (positional        resolution of the detection of the interrupt), not only can the        diode lying exactly opposite the currently operating receiver        (pair 340) be turned on, but also its direct neighbor. The        emitter on time then decreases to ⅓ of the receiver on time.        Other time sequences/positional combinations are also possible.        To touch the interactive surface, usually only one finger (index        finger) is used. The index finger of small children has an        average diameter of 10 mm, that of adults approximately 18 mm.        The distance of the light barriers equals 10 mm in the        x-direction and y-direction. In the normal case, an adult always        interrupts more than one light barrier and can thus be detected        at 100%. In the worst case, a small child can hold a finger        between two light barriers, so that residual light radiation        like from one-sided screen shading is always still seen by the        receiver.

To achieve a higher detection likelihood for smaller objects, which caninterrupt the beam path, the following controls of the receiver andemitter are possible. Starting with emitter LEDs with 5 mm φ, 10 mmdistance to neighbor LED, and a beam angle of ±8°, the following resultswere calculated for the statistical evaluation to resolve an interruptwith 100% reliability at any position within the active region(resolution of the position <±1.5 mm).

a) Turned on during the integration time are:

-   -   receiver n and emitter n continuously: the finger thickness must        be at least 15 mm in the entire interactive region to be        detected at 100% with a resolution of ±1.5 mm with additional        evaluation in the central module 140 (additional evaluation is        described farther below).

b) The emitters n−1, n, and n+1 are turned on one after the other duringthe integration time of the receiver n. The receiver signals areevaluated as a function of which emitter is currently active.

c) The emitters n−3, n−1, n, n+1, n+3 are turned on one after the otherduring the integration time of the receiver n. The receiver signals areevaluated as a function of which emitter is currently active.

Other arbitrary combinations of emitter control relative to the receiverare conceivable. The burst on-time period is here lengthenedcorrespondingly. Because the total distance between the emitter andreceiver arrays is usually greater than the projected image and thus thedesired interactive region, in most cases the control according tomethod b) makes the most sense. However, by means of microcontrollertechnology, if desired, version a) or c) can also be set. Other settingsof the total control are possible. All controls except 1) allow thereliable detection of a finger thickness>10 mm.

-   -   7) If the emitter and receiver units (100, 110, 120, 130) are        located at a large distance to each other and directly in front        of a very reflective surface (display window), then in addition        to the electronic regulation, the emitter and receiver modules        (300, 310) can also be installed in a housing, such that a        screen is created only in the surface of the projection, which        prevents the emitted light of the emitter diodes from reaching        the reflective surface, and thus prevents beam interruption, and        thus detection. This screen can also be mounted as a separate        part.

8) In addition to the combination of relative emitter changeover withreference to the integration of a receiver, which significantlyincreases the detection likelihood of smaller objects, a basicstatistical analysis concerning interruptions of the light barriers inposition and time is performed in the central module 140. This producesa higher resolution of the scanning up to approximately 1 mm. An averagevalue formation of the interruptions over 3 adjacent light barriers andin addition a time analysis over three scans in sequence permit thereliable detection of the user and the input location. In addition,short interruptions, e.g., insects, are excluded. Longer interruptions(opaque object on a light barrier area) can also be filtered out afterthe recognition time (20-40 s). In addition, an event is interpreted astrue only if x and y light barriers are interrupted for a minimum time.

-   -   9) The central module 140 emulates a standard serial mouse        relative to the control computer (PC) 220. Thus, this system can        be used immediately for all operating systems (e.g., Windows        95/98/2000 or Linux) and computer types (e.g., PCs,        workstations). If the user leaves the interactive region at a        position x₁, y₁, then the pressing of the left mouse button at        this position is reported to the control computer by the central        module. Because the central module is built with a        microcontroller, the emulation of the direct output of        x-coordinates and y-coordinates for video games or a PS2 mouse        can also be executed in firmware. Other interface protocols can        be loaded by the control computer at any time into the central        module. In addition to the mouse emulation, the central module        140 can emulate a standard IBM keyboard (150, 160) if desired.

A typical user input and its detection then look like this:

The user brings his finger close to the touch-sensitive surface (displaywindow) to touch an image region displayed by the projector. After acertain cycling of the scanning of all emitter and receiver diodes,several receiver diodes in the horizontal and vertical directiondetermine a light interruption. This information is converted in thecentral module 140 into a position of the user interruption and can betransmitted to the control computer, e.g., as the position of the mousepointer. For the next scan cycle, the focus of the interrupt is possiblylocated at a different position (because one scan only lasts {fraction(1/20)} of a second, the position of the interrupt changes only slowly).If after a certain scan an interruption is no longer determined, thenthe user has removed his finger from the sensitive zone. This action canbe transmitted to the control computer from the central module as amouse click. Then the control computer can display new image contentscorresponding to the mouse click on the touch-sensitive surface by theprojector.

According to the invention, there are also configurations with anunequal number of emitter and receiver diodes in the emitter andreceiver units. For large distances from the emitter unit to thetouch-sensitive surface, emitter diodes can thus be spared. Theresolution is then determined by the distance of the receiver diodes.

Another configuration according to the invention consists in that theemitter and receiver diodes are not arranged in different modules andemitter and receiver units, but instead alternating or in parallel onone side. On the opposite side, there is then either a reflective orabsorbing unit. In the first case, the detection is completely analogousto the description above. In the second case, the light back-scatteredby the user input (typically a finger) is used for detection (no lightbarrier interrupt is detected, instead the light barrier closing isdetected). The absorption device in the opposite region prevents anunintended closing of the light barriers. The control of adjacentemitter and receiver diodes otherwise follows the path described inpoints 1-8.

A preferred configuration of the installation of the touch-sensitivesurface is that shown in FIG. 1. Here, a data and video projectorilluminates from behind a rear-projection surface (normal focusingscreen, holographic rear-projection screen, e.g., HoloPro© from Pronovafor better suppression of ambient light) located behind a displaywindow. The touch-sensitive surface is built on the display window. Theholders of the emitter and receiver units can be “hidden” in the frameof the display window screen. For a typical projection surface of 1.6m², a transmission of the focusing screen of 50%, a light-amplificationfactor of the focusing screen in the forward direction of 2, an ambientbrightness on the display window of 2000 lx (shaded outside area), and adegree of reflection for this light of approximately 35%, a projectorwith an optical power of approximately 2300 ANSII lumens is required toachieve twice as much light as the ambient light on the focusing screen.For the use of a HoloPro™ screen, this ratio is even more favorable. Atouch-sensitive display window can be used for advertisement anywhere inan outside area, whether in pedestrian zones, at exhibitions, in autodealers, etc. Other applications of the touch-sensitive surface arelarge, enclosed rear-projection boxes (multi-active boxes) or smallerinformation terminals in railroad stations or airports.

List of Reference Symbols

FIG. 1

Key:

-   -   1 Glass panel of the display window    -   2 Projection surface    -   3 Strip with receiver modules    -   4 Strip with receiver modules    -   5 Strip with emitter modules    -   6 Strip with emitter modules    -   7 Video-data projector    -   8 Decoration        FIG. 2        Key:    -   100 Strip with emitter modules    -   110 Strip with receiver modules    -   120 Strip with emitter modules    -   130 Strip with receiver modules    -   140 Central module    -   150 Mouse output    -   160 Keyboard output    -   170 Film with keyboard image    -   175 Not used area    -   180 Projection surface (image surface)    -   190 Touch-sensitive area    -   200 Video-data projector    -   210 Mouse-keyboard-monitor changeover switch    -   220 Computer    -   230 Monitor    -   240 Keyboard    -   250 Mouse    -   260 Printer    -   270 Card reader    -   280 LAN connection        FIG. 3        Key:    -   300 Emitter module    -   310 Receiver module    -   320 Emitter diodes    -   330 Receiver phototransistors or diodes    -   340 Emitter-receiver pair    -   350 IR light beam

1. A touch-sensitive region on a display device for detecting a userinput, comprising: emitter diodes for outputting light; receiverdiodes/phototransistors for detecting the light, the emitter diodes andreceiver diodes/phototransistors being arranged in vertical andhorizontal emitter and receiver units set opposite to each other, one ofthe emitter diodes and one of the receiver diodes/phototransistors beingoptically set in a direct paired relationship to each other; and acentral module; wherein the detection of a user input is realizedthrough continuously repeating time-sequenced and position-sequencedon-and-off switching of individual emitter diodes and receiverdiodes/phototransistors; wherein one of the emitter diodes and one ofthe receiver diodes/phototransistors are controlled in pairs; andwherein for evaluating and increasing the resolution, the signals of theemitter diodes are referenced, adjacent to the emitter diodes, and allelectrical signals of the receiver diodes/phototransistors are assembledinto the central module, and also the emitter diodes are controlled fromthe Central module, such that the emitter diodes output a plurality ofpulses, whose integrative, quantitative evaluation is a measure of theposition of the interruption of a light barrier during an evaluationperiod and provides information on the position of the interruptionrelative to the emitter diodes.
 2. A touch-sensitive region according toclaim 1, characterized in that the emitter diodes are operated duringtheir short on-time with higher power than their nominal continuouspower.
 3. A touch-sensitive region according to claim 1, characterizedin that the wavelength of the applied electromagnetic radiation is inthe infrared range of the spectrum and the emitter diodes and receiverdiodes/phototransistors are emitting and receiving semiconductorelements.
 4. A touch-sensitive region according to claim 1,characterized in that the emitter diodes are operated with a burstsignal during their on time, which means that the electrical alternatingsignal controlling them has a higher frequency f than the alternatingfrequency of the emitter diodes controlled one after the other; whereinfor faster saturation, measures, such as increasing the start-up voltageamplitude/voltage rise time and necessary discharge of charge carriersfrom the emitter diodes after the saturation pulse, are used.
 5. Atouch-sensitive region according to claim 1, characterized in that theamplifier circuit of the receiver diodes or phototransistors has a largeamplification at the burst frequency f and otherwise enables a highattenuation through an inductive operating resistor followed by anintegrator.
 6. A touch-sensitive region according to claim 1,characterized in that not only the emitter diodes arranged optically inpairs with a receiver diode or phototransistor are active during the ontime of the receiver diode or phototransistor, but adjacent emitterdiodes are also active.
 7. A touch-sensitive region according to claim1, characterized in that an optical aperture is arranged in front of theemitter diodes and receiver diodes or phototransistors.
 8. Atouch-sensitive region according to claim 1, characterized in that theoptical paired relationship of emitter diodes and receiver diodes orphototransistors involves oppositely positioned emitter diodes andreceiver diodes or phototransistors in opposing emitter and receiverunits.
 9. A touch-sensitive region according to claim 1, characterizedin that the optically paired relationship of the emitter diodes andreceiver diodes or phototransistors involves emitter diodes and receiverdiodes or phototransistors positioned one next to the other in a mixedemitter and receiver unit and an oppositely positioned mirror surface.10. A touch-sensitive region according to claim 1, characterized in thatthe optical relationship of the emitter diodes and receiver diodes orphototransistors involves emitter diodes and receiver diodes orphototransistors positioned one next to the other in a mixed emitter andreceiver unit and an oppositely positioned absorbing surface.
 11. Atouch-sensitive region according to claim 1, characterized in that thetotal number of emitter diodes in the emitter units is exactly equal toor not equal to the number of receiver diodes or phototransistors in thereceiver units.
 12. A touch-sensitive region according to claim 1,characterized in that a microprocessor of the central module calculatesthe position of the user input from digital receiver module signals bymeans of a statistical analysis method.
 13. A touch-sensitive regionaccording to claim 1, characterized in that the central module cansimulate any arbitrary interface relative to an attached computer.
 14. Atouch-sensitive region according to claim 2, characterized in that thewavelength of the applied electromagnetic radiation is in the infraredrange of the spectrum and the emitter diodes and receiverdiodes/phototransistors are emitting and receiving semiconductorelements.
 15. A touch-sensitive region according to claim 2,characterized in that the emitter diodes are operated with a burstsignal during their on time, which means that the electrical alternatingsignal controlling them has a higher frequency f than the alternatingfrequency of the emitter diodes controlled one after the other; whereinfor faster saturation, measures, such as increasing the start-up voltageamplitude/voltage rise time and necessary discharge of charge carriersfrom the emitter diodes after the saturation pulse, are used.
 16. Atouch-sensitive region according to claim 3, characterized in that theemitter diodes are operated with a burst signal during their on time,which means that the electrical alternating signal controlling them hasa higher frequency f than the alternating frequency of the emitterdiodes controlled one after the other; wherein for faster saturation,measures, such as increasing the start-up voltage amplitude/voltage risetime and necessary discharge of charge carriers from the emitter diodesafter the saturation pulse, are used.
 17. A touch-sensitive regionaccording to claim 2, characterized in that the amplifier circuit of thereceiver diodes or phototransistors has a large amplification at theburst frequency f and otherwise enables a high attenuation through aninductive operating resistor followed by an integrator.
 18. Atouch-sensitive region according to claim 3, characterized in that theamplifier circuit of the receiver diodes or phototransistors has a largeamplification at the burst frequency f and otherwise enables a highattenuation through an inductive operating resistor followed by anintegrator.
 19. A touch-sensitive region according to claim 4,characterized in that the amplifier circuit of the receiver diodes orphototransistors has a large amplification at the burst frequency f andotherwise enables a high attenuation through an inductive operatingresistor followed by an integrator.
 20. A touch-sensitive regionaccording to claim 2, characterized in that not only the emitter diodesarranged optically in pairs with a receiver diode or phototransistor areactive during the on time of the receiver diode or phototransistor, butadjacent emitter diodes are also active.